Lesson B2 · Upper-intermediate Grammar

The Missing Picnic Box: Past Modal Practice

Use a fictional evidence log to separate past explanations, missed chances and useful hindsight.

10 min read 1,748 words Updated Oct 28, 2026

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B2 • About 30 minutes. Select a modal from the evidence and communicative purpose. Distinguish what happened from what might have happened. Separate an unrealised option from an uncertain explanation. Write constructive hindsight without unsupported accusations.

Known: blue box photographed in car at 09:10. Unknown: current location and later handler. Possible: stayed in boot. Hindsight: should have checked. Expected drinks arrival: still unconfirmed. — Instructional visual. A selectable-text equivalent appears in the resource.

Read the evidence log

The community picnic story is fictional. At 8:45, Sara packed a blue box with cups and napkins. At 9:10, a genuine time-stamped photograph showed the closed box in the back of Jules’s car. Jules drove to the park and arrived at 9:35. At 9:40, the group noticed that the box was not on their picnic table. The table had been brought into the park at 9:30, so the box could not have been sitting on that table in the park at nine. Nobody had checked the car’s boot since the group arrived. Sara wrote, “The box could have stayed in the car. Let’s look there before deciding what happened.” Jules replied, “We could have checked every bag before leaving, but we were in a hurry and did not.” The organiser said, “The delivery of extra drinks should have arrived by now; the estimate was 9:30. I have not confirmed it.” No message says that anyone stole the box. No message confirms the drinks delivery. The group has a location question to investigate, not evidence of deliberate wrongdoing.

Five confirmed facts: packed at 8:45; photographed in the car at 9:10; car arrived at 9:35; box absent from the table at 9:40; boot not yet checked. Unknowns: current box location, who last handled it after the photo, and whether the extra drinks arrived.

Separate facts from explanations

Facts are explicitly recorded. Inferences interpret those facts. The blue box was in the photographed location at 9:10; it may still be in the car, but the photo alone cannot establish its location thirty minutes later. If you write a modal perfect, make the relevant time visible and match the strength to the evidence.

The opportunity sentence supplies its own outcome: the group did not check every bag. The drinks sentence supplies only an expectation. For open answers, may have, might have and could have can all be suitable ways of keeping an explanation cautious. The controlled choices below specify the intended job so that you can explain your selection.

Explanation checks

Choose the interpretation supported by the exact evidence.

Answer on paper, then open the explanations below. Enable JavaScript to check answers here.

1 The genuine 9:10 photo shows the blue box in the car. Choose a strong inference about that time.

Choose one answer.

The box must have been in the car at 9:10. The box must have stayed in the car all morning.

Answer and explanation

The box must have been in the car at 9:10.

The photo supports the specific photographed time. It does not show the whole morning.

2 Nobody has checked the boot. Choose a suitably cautious explanation.

Choose one answer.

Jules must have stolen the box. The box might have stayed in the car.

Answer and explanation

The box might have stayed in the car.

The unchecked boot leaves a plausible location unresolved. There is no evidence for theft or blame.

3 The table entered the park at 9:30. Which rejects an impossible earlier location?

Choose one answer.

The box cannot have been on that table in the park at nine. The box cannot have been in any car at nine.

Answer and explanation

The box cannot have been on that table in the park at nine.

The correct answer is limited to the stated table, place and time. Nothing in the log rules out a car location at nine; the later photo places the box in Jules’s car at 9:10.

4 At 9:40 the box is absent from the table. Which inference is justified?

Choose one answer.

Someone definitely destroyed it. Someone may have left it elsewhere.

Answer and explanation

Someone may have left it elsewhere.

Absence from one place permits possible alternatives, not a definite destructive action.

5 Which sentence carefully distinguishes a past fact from an unknown later location?

Choose one answer.

The box was in the car at 9:10, but it might have been moved later. The box was in the car at 9:10, so it must still be there.

Answer and explanation

The box was in the car at 9:10, but it might have been moved later.

The photograph establishes an earlier location only. The correct answer preserves uncertainty about later events.

Opportunity or explanation?

Use the continuation, not could have alone.

Answer on paper, then open the explanations below. Enable JavaScript to check answers here.

6 “The box could have stayed in the car; nobody has checked yet.”

Choose one answer.

known unused opportunity uncertain explanation

Answer and explanation

uncertain explanation

Nobody has checked leaves the location unknown. There is no confirmed alternative outcome.

7 “We could have checked every bag, but we did not.”

Choose one answer.

unused opportunity unknown explanation

Answer and explanation

unused opportunity

But we did not explicitly states that the available check was not performed.

8 “Sara could have brought the box.” Without more context, what can you conclude?

Choose one answer.

It definitely means she brought it. The meaning may be ambiguous. It definitely means she did not bring it.

Answer and explanation

The meaning may be ambiguous.

The sentence can describe a possible explanation or an available option. A continuation is needed to settle the intended reading.

Helpful hindsight and expectation

Choose the job and wording that fit the log.

Answer on paper, then open the explanations below. Enable JavaScript to check answers here.

9 The group skipped the bag check. Which gives constructive hindsight?

Choose one answer.

We should have checked the bags before leaving. We must have checked every bag.

Answer and explanation

We should have checked the bags before leaving.

It names the missed useful action without contradicting the group’s admission that they did not check.

10 “The drinks should have arrived by now; the estimate was 9:30.” What is expressed?

Choose one answer.

an expectation confirmed arrival an accusation of theft

Answer and explanation

an expectation

The estimate supports expected timing. The organiser explicitly says delivery is unconfirmed.

11 They did not label the two similar blue boxes. Which is a suitable hypothetical hindsight sentence about this additional scenario?

Choose one answer.

They should have labelled the boxes. They might have labelled the boxes, so it is certain.

Answer and explanation

They should have labelled the boxes.

The stated failure to label supports advice in hindsight. This additional practice scenario is separate from the main log.

12 Choose the clearest report of the unconfirmed drinks outcome.

Choose one answer.

The drinks have arrived because they should have. The drinks should have arrived, but we need to check.

Answer and explanation

The drinks should have arrived, but we need to check.

Expectation and actual delivery are different. The correct answer preserves the need for confirmation.

Repair the group message

Repair a form or reduce an unsupported claim.

Answer on paper, then open the explanations below. Enable JavaScript to check answers here.

13 Correct: “The box might have went elsewhere.” Your answer

Answer and explanation

The box might have gone elsewhere.

Also accepted: The box might have gone elsewhere

Have requires the past participle gone, not the past-simple went.

14 Correct: “We should of checked the bags.” Your answer

Answer and explanation

We should have checked the bags.

Also accepted: We should've checked the bags.; We should’ve checked the bags.; We should have checked the bags; We should've checked the bags; We should’ve checked the bags

Use modal + have + past participle. The spoken contraction should’ve is also standard.

15 Repair the unsupported claim “Jules must have taken it away deliberately.”

Choose one answer.

The box might have been moved; we do not know by whom or why. Jules definitely took it away deliberately.

Answer and explanation

The box might have been moved; we do not know by whom or why.

The evidence does not identify a later handler or intention. The repair preserves uncertainty instead of accusing Jules.

16 Correct the verb phrase and write the complete sentence: “It must had been in the car at 9:10.” Your answer

Answer and explanation

It must have been in the car at 9:10.

Also accepted: It must have been in the car at 9:10

Must takes have, then the past participle been. The reliable photo supports this specific location and time.

Write, compare and revise

Your turn · self-review

Independent writing

Write your own response first, then compare the model and use the self-review checklist below. The model is one possible answer, not a script to copy.

Practice only. Your writing stays on this page; it is not submitted or saved.

1Write a 100–130-word group update. Include one confirmed fact, one justified possibility and two constructive hindsight points. Keep the current location and drinks delivery unconfirmed. Suggest a next check without blaming anyone.
Model answer and explanation
The blue picnic box was in Jules’s car at 9:10, as the time-stamped photograph shows. It was not on our table at 9:40, and nobody has checked the boot since we arrived. The box might have stayed in the car, so that is a sensible place to look first. We should have checked the bags before leaving, and we should have confirmed who was carrying the box into the park. Those checks would have made the handover clearer. We do not yet know who last moved it or where it is now. The extra drinks should have arrived according to the estimate, but their delivery still needs confirmation.

Self-review and transfer

The model quotes a known time and location, gives a cautious possibility and names two useful hindsight checks. Its second hindsight point is a suggested improvement, not a claim that the source recorded a particular handover. Check whether your update distinguishes evidence from recommendation. Remove any statement about theft, motive or current location unless the log supports it. Replacing must with might can reduce certainty, but you must also remove invented details.

Companion resource: Past Modals: Must Have, Might Have, Could Have and Should Have.

Related references for further study: Library Rules: Must, Have To and Should Practice; How Sure Can We Be About This Claim?; Why the Event Started Late: Third Conditional Practice.